Re-refining used automotive lubricating oil

ABSTRACT

This patent describes a process for re-refining waste automotive lubricating oil and similar waste hydrocarbon oils, which employs a novel sequence of steps including treatment with a saturated hydrocarbon solvent, followed by vacuum distillation, followed by catalytic hydrogenation.

United States Patent 191 Cutler et al.

[ RE-REFINING USED AUTOMOTIVE LUBRICATING OIL [75] Inventors: Louis E. Cutler; Edward T. Cutler.

both of Merion Pa.

[73] Assignee: Pilot Research & Development 01.,

Merion Station, Pa.

[22] Filed: Dec. 12. 1974 1 Appl. No.: 532,167

Related U.S. Application Data [63] Continuation-impart of Ser. No. 489779 Jul I8.

1974 abandoned [52] US. Cl. .1 208/180; 208/179; 208/[84 [5 [1 Int. Cl. C10M 11/00 [58} Field of Search 208/l79, 180 184 [56] References Cited UNITED STATES PATENTS 1.241.667 lU/l9l7 Elliott BUR/I79 Nov. 11, 1975 Primary Ev\'un1inerDelbert E. Gantz Amifiluu! E.\'um1'ner.luanita M, Nelson [57] ABSTRACT This patent describes a process for re-refining waste automotive lubricating oil and similar waste h \'drocarhon oils. which employs a novel sequence of steps ineluding treatment with a saturated hydrocarbon solvent. followed by vacuum distillation. followed by catalytic h drogenation.

3 Claims. No Drawings RE-REFINING USED AUTOMOTIVE LUBRICATING OIL This application is a continuation-in-part of application Ser. No. 489,779, filed July 18, i974, and now abandoned.

The process of this invention is a pollution-free way to make the highest quality automotive lubricating oil at the lowest cost from waste crankcase oil (hereafter called WCCO) and similar waste hydrocarbon oils. Widespread use of the process of this invention can satisfy 25-50% of this country's automotive lube oil needs, conserve a limited natural resource, and prevent pollution.

The composition of WCCO in the United States today is:

1-6% Light ends (b.p. up to 350F. at 760 torr) 10-15% Heavy ends (b.p. 350-650F. at 760 torr) 60-70% Lube stock (b.p. 650-800F. at 760 torr) O-l% Bright stock (b.p. 800-950F. at 760 torr) l3% Particulates (mostly 2 dia., principally C,

Pb, P and Ca) 0l0% Water 7-l Additives 5-8% Oil oxidation products Previous re-refining processes have had serious difficulties because lube oil additives are difficult to remove from WCCO, and interfere with the removal of other impurities. Re-refining with sulfuric acid creates a considerable volume of acid sludge which is difficult to properly dispose of. Re-refining with any combination of caustic soda, caustic silicate, slalted lime, and deemulsifiers yields undependable results and creates a considerable amount of noxious sludge containing significant amounts of oil. Re-refining with a process whose first step is vacuum distillation creates severe equipment maintenance problems and oil loss. Rerefining with polar organic solvents such as chlorex, selecto, phenol, furfural, and various alkanol and alkanol-water mixtures is inferior to treatment with propane (the preferred solvent of this invention) because a considerable amount of lube oil is lost, 3-5 times more heat is needed in the recovery step to distill a given volume of polar solvent, and smaller amounts of WCCO impurities are removed. Refining by direct catalytic hydrogenation of dehydrated WCCO, and re-refining by propane treatment of dry WCCO followed by high temperature bauxite treatment yield finished oil of inferior quality. Re-refining by high temperature WCCO treatment, followed by clay treatment, filtration, and catalytic hydrogenation, and re-refining by propane treatment of dry WCCO followed by catalytic hydrogenation yield finished oil of satisfactory quality; but, compared to the process of this invention, hydrogenation pressure and temperature must be higher, hydrogenation L.H.S.V. must be lower, hydrogen consumption is at least doubled, hydrogenation catalyst life is reduced, larger hydrogenation capacity is required, and more fuel from external sources is required. In addition, little or no lube oil fractionation is carried out to separate the light ends, heavy ends, lube stock, and bright stock.

The process of this invention consists of the following steps:

1. Screen out large pieces of debris and dehydrate the oil.

2. Mix the dry oil with l-] 5 (preferably 4-6) times its volume of a saturated hydrocarbon selected from the group consisting of ethane, propane, butane, pentane,

hexane, and mixtures thereof (preferably propane). Keep the mix liquid under pressure at a temperature near but below its critical point. In the case of propane, we prefer temperatures of l-l90F. at 600-700 psig. Settle the mix, drain off the bottoms, and separate the clarified oil-solvent mix. The bottoms can be burned to supply process heat. A special scrubber must be used to remove heavy metal particulates from the combustion gases.

3. Strip the solvent from the clarified oil-solvent mix of step 2, condense it and store for reuse. Collect the stripped oil.

4. Vacuum distill the stripped oil of step 3 at a pressure no greater than 10 torr and a temperature no greater than 650F., distilling over all but l0-l5% of the charge stock. Fractionate the distillate. No maintenance or yield problems result from vacuum distilling this material. The vacuum bottoms can be burned to supply process heat. No special scrubber is needed.

5. Hydrogenate the condensed hot oil fractions over a catalyst consisting of one or more Group V] and/or Vlll metal oxides or sulfides at 500-800F. (preferably 600'.00F.), 500-1000 psig (preferably 600-700 psig), and L.H.S.V. 0.5-2.0 (preferably L0).

6. Strip the hydrogenated oil fractions of hydrogen, reduction products, and light ends.

7. Cool and filter the oil.

Each step of the process of this invention is known, but the novel sequence of steps has not been stated or appreciated till now. The precipitative hydrocarbon step removes 70-80% of the original WCCO impurities. Impurities precipitated by the hydrocarbon solvent consist of high molecular weight additives. additive fragments, and oil oxidation products, plus high density particulates. The vacuum distillation step removes l0-l 5% of the original WCCO impurities and fractionates the oil. Impurities eliminated in the vacuum bottoms consist of medium molecular weight additives, additive fragments, and oil oxidation products, plus low molecular weight salts, acids, and colloidal solids. The hydrogenation step removes the last IO-ISX' of the original WCCO impurities by chemically transforming them into hydrocarbons having molecular weights equal to or less than oil, plus H 5, H 0, and NH;,. lmpurities removed by the hydrogenation step consist of low molecular weight additives, additive fragments, and oil oxidation products. The important features of the process of this invention are:

1. Each step removes a significant amount of impurities which are not easily removed by the previous step.

2. Each step removes a significant amount of impurities which are not easily removed by the step that follows.

3. All impurities are dependably removed.

4. Impurities are removed in the form of easily burned fuels.

5. Processing cost is the lowest of any known process.

6. Equipment maintenance costs are very low.

7. There is little oil loss and no pollution.

8. The finished oil is equal to or better than virgin lube oil in quality.

An example of the process of this invention follows:

A sample of WCCO was heated to 350F. 2% light ends and water were removed. 500 ml of the dry WCCO were placed in a pressure vessel with 2500 ml of propane. The mix was shaken, heated to lF., and allowed to settle one hour. Then the propane bottoms,

representing 12% by weight (10% by volume) of the dry WCCO. were drained out of the pressure vessel. The clarified propane-oil mix was decanted and depropanized, then the 450 ml of propane-treated oil was subjected to a nitrogen-vacuum distillation at 10 torr. The first l% of distillate was considered to be heavy ends. the l0-90% cut (b.p. 490620F. at 10 torr) was considered to be in the lube range. the last 10% was left in the pot, The lube oil cut was hydrogenated in a pressure vessel under the following conditions:

oil:eatalyst volume ratio=l eata|yst=Houdry HR-80l cobalt-molybdenum catalyst. 25% sulfided temperature=650F.

reaction time=l hour H pressure=650 psig Then it was lightly stripped to remove l2% light ends, reduction products and hydrogen. and filtered to remove catalyst fines. Properties of the finished lube oil are shown in Table 1.

Table 1 Properties of WCCO and finished lube oil made by the process of this invention Table l-eontinued Properties of WCCO and finished lube oil made by the process of this nvention WCCO Finished lube nitrogen 0.l'l' 0.05%

As the invention, we claim:

1. A process for re-refining waste crankcase oil and similar waste hydrocarbon oils consisting of the following consecutive steps:

a. Screen out large pieces of debris and dehydrate the oil;

b. Mix the dry oil with l to 15 times its volume of a saturated hydrocarbon selected from the group consisting of ethane. propane. butane pentane, hexane. and mixtures thereof while keeping the mix liquid under pressure at a temperature near but below its critical point;

e. Settle the mix, drain off the bottoms, and separate the clarified oil-solvent mix;

d. Strip the solvent from the clarified oil-solvent mix of step (C), condense it. and store for reuse;

e, Vacuum distill the stripped oil of step (d) at a pressure no greater than 10 torr and a temperature no greater than 650F., distilling over all but l0-l5% of the charge stock and fractionate the distillate;

f. Hydrogenate the condensed hot oil fraction over a catalyst consisting of one or more Group VI and/or Vlll metal oxides or sulfides at 500-800F, 500-1000 psig, and L.H.S.V. of 0.5-2.0;

g. Strip the hydrogenated oil fractions of hydrogen,

reduction products, and light ends;

h. Cool the hydrogenated oil and filter it.

2. The process of claim I wherein the saturated hydrocarbon in step (b) is propane, employed in an amount equal to 4-6 times the volume of the dry oil at a temperature of l-l90F. and a pressure of 600-700 psig.

3. The process of claim 1 wherein the hydrogenation step (f) is carried out at 600700F., 600-700 psig, and L.H.S.V. 1.0. 

1. A PROCESS FOR RE-REFINING WASTE CRANKCASE OIL AND SIMILAR WASTE HYDROCARBON OILS CONSISTING OF THE FLLOWING CONSECUTIVE STEPS: A. SCREEN OUT LARGE PIECES OF DEBRIS AND DEHYDRATI THE OIL, B. MIX THE DRY OIL WITH 1 TO 15 TIMES ITW VOLUME OF A SATURATED HYDROCARBON SLELCTED FROM THE GROUP CONSISTING OF ETHANE, PROPANE, BUTANE, PENTANE, HEXANE, AND MEXTURES THEREOF WHILE KEEPING THE MIX LIQUID PRESSURE AT A TEMPERATURE NEAR BUT BELOW ITS CRITICAL POINT, C. SETTLE THE MIX, DRAIN OFF THE BOTTOMS, AND SEPARATE THE CLARIFIED OIL-SOLVENT MEX, D. STRIP THE SOLVENT FROM THE CLARIFIED OIL-SOLVENT MEX OF STEP (C), CONDENSE IT, AND STORE FOR REUSE, E. VACUUM DISTILL THE STRIPPED OIL OF STEP (D) AT A PRESSURE NO GREATER THAN 10 TORR AND A TEMPERATURE NO GREATER THAN 650*F., DISTILLING OVER ALL BUT 10-15% OF THE CHARGE STOCK AND FRACTIONATE THE DISTILLATE, F. HYDROGENATE THE CONDENSED HOT OIL FRACTION OVER A CATALYST CONSISTING OF ONE OR MORE GROUP VI AND/OR VIII METAL OXIDES OR SULFIDES AT 500*-800*F, 500-1000 PSIG, AND L.H.S.V. OF 0.5-2.0, G. STRIP THE HYDROGENATED OIL FRACTIONS OF HYDROGEN, REDUCTION PRODUCTS, AND HIGHT ENDS, H. COOL THE HYDROGENATED OIL AND FILTER IT.
 2. The process of claim 1 wherein the saturated hydrocarbon in step (b) is propane, employed in an amount equal to 4-6 times the volume of the dry oil at a temperature of 180*-190*F. and a pressure of 600-700 psig.
 3. The process of claim 1 wherein the hydrogenation step (f) is carried out at 600*-700*F., 600-700 psig, and L.H.S.V. 1.0. 